US officials: Iran invited for first time to join international talks on Syria's future

US officials say Iran is being invited to participate for the first time in international talks aimed at peacefully ending Syria's four-year civil war.

The next diplomatic round starts Thursday in Vienna. Secretary of State John Kerry, Russian Foreign Minister Sergey Lavrov and several top European and Arab diplomats will attend.

The officials, who weren't authorized to speak on the record and demanded anonymity, said Russia delivered the invitation; Iran has yet to respond.